Method and apparatus for handling sidelink communication according to type of handover

ABSTRACT

The disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method and apparatus for handling sidelink communication according to type of handover are provided.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. §119(a) of a Korean patent application number 10-2020-0137784, filed onOct. 22, 2020, in the Korean Intellectual Property Office, thedisclosure of which is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a wireless communication system. Moreparticularly, the disclosure relates to an apparatus, a method and asystem of handling sidelink (SL) communication according to type ofhandover in wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5^(th) generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post Long-Term Evolution(LTE) System’. The 5G communication system is considered to beimplemented in higher frequency (millimeter (mm) Wave) bands, e.g., 60gigahertz (GHz) bands, so as to accomplish higher data rates. Todecrease propagation loss of the radio waves and increase thetransmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems. In addition, in 5G communication systems,development for system network improvement is under way based onadvanced small cells, cloud Radio Access Networks (RANs), ultra-densenetworks, device-to-device (D2D) communication, wireless backhaul,moving network, cooperative communication, Coordinated Multi-Points(CoMP), reception-end interference cancellation and the like. In the 5Gsystem, Hybrid frequency-shift keying (FSK) and quadrature amplitudemodulation (QAM) Modulation (FQAM) and sliding window superpositioncoding (SWSC) as an advanced coding modulation (ACM), and filter bankmulti carrier (FBMC), non-orthogonal multiple access (NOMA), and sparsecode multiple access (SCMA) as an advanced access technology have beendeveloped.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

Meanwhile, there have been various studies on sidelink (SL)communication handling in wireless communication system recently.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea communication method and system for converging a fifth generation (5G)communication system for supporting higher data rates beyond a fourthgeneration (4G).

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a method performed by aterminal is provided. The method includes receiving, from a source basestation, a first radio resource control (RRC) message includinginformation on sidelink parameters for sidelink communication, applyingthe sidelink parameters included in the first RRC message to a firstmedium access control (MAC) entity associated with the source basestation, receiving, from the source base station, a second RRC messageincluding reconfiguration with synchronization information andinformation on sidelink parameters for sidelink communication,generating a second MAC entity associated with a target base station, incase that at least one dual active protocol stack (DAPS) bearer isconfigured in the second RRC message, applying the sidelink parametersincluded in the second RRC message to the second MAC entity associatedwith the target base station, and performing a random access procedurewith the target base station based on the second RRC message.

In accordance with another aspect of the disclosure, a method performedby a base station is provided. The method includes transmitting, to aterminal, a first radio resource control (RRC) message includinginformation on sidelink parameters for sidelink communication, thesidelink parameters included in the first RRC message are for a firstmedium access control (MAC) entity associated with the source basestation, and transmitting, to the terminal, a second RRC messageincluding reconfiguration with synchronization information andinformation on sidelink parameters for sidelink communication, thesidelink parameters included in the second RRC message are for a secondMAC entity associated with a target base station, wherein the second MACentity is generated for the target base station, in case that at leastone dual active protocol stack (DAPS) bearer is configured in the secondRRC message, and wherein a random access procedure is performed betweenthe terminal and the target base station based on the second RRCmessage.

In accordance with another aspect of the disclosure, a terminal isprovided. The terminal includes a transceiver, and a controllerconfigured to receive, from a source base station, a first radioresource control (RRC) message including information on sidelinkparameters for sidelink communication, apply the sidelink parametersincluded in the first RRC message to a first medium access control (MAC)entity associated with the source base station, receive, from the sourcebase station, a second RRC message including reconfiguration withsynchronization information and information on sidelink parameters forsidelink communication, generate a second MAC entity associated with atarget base station, in case that at least one dual active protocolstack (DAPS) bearer is configured in the second RRC message, apply thesidelink parameters included in the second RRC message to the second MACentity associated with the target base station, and perform a randomaccess procedure with the target base station based on the second RRCmessage.

In accordance with another aspect of the disclosure, a base station isprovided. The base station includes a transceiver and a controllerconfigured to transmit, to a terminal, a first radio resource control(RRC) message including information on sidelink parameters for sidelinkcommunication, the sidelink parameters included in the first RRC messageare for a first medium access control (MAC) entity associated with thesource base station, and transmit, to the terminal, a second RRC messageincluding reconfiguration with synchronization information andinformation on sidelink parameters for sidelink communication, thesidelink parameters included in the second RRC message are for a secondMAC entity associated with a target base station, wherein the second MACentity is generated for the target base station, in case that at leastone dual active protocol stack (DAPS) bearer is configured in the secondRRC message, and wherein a random access procedure is performed betweenthe terminal and the target base station based on the second RRCmessage.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates an example of small data transmission according to anembodiment of the disclosure;

FIG. 2 illustrates another example of small data transmission accordingto an embodiment of the disclosure;

FIG. 3 illustrates another example of small data transmission accordingto an embodiment of the disclosure;

FIG. 4 illustrates an architecture supporting PC5 interface according toan embodiment of the disclosure;

FIG. 5A illustrates an example of a sidelink (SL) communication handlingaccording to an embodiment of the disclosure;

FIG. 5B illustrates another example of an SL communication handlingaccording to an embodiment of the disclosure;

FIG. 6 illustrates an example of paging collision between multipleuniversal subscriber identity module (MUSIM) according to an embodimentof the disclosure;

FIG. 7 illustrates another example of paging collision between multipleuniversal subscriber identity module (MUSIM) according to an embodimentof the disclosure;

FIG. 8 illustrates another example of paging collision between multipleuniversal subscriber identity module (MUSIM) according to an embodimentof the disclosure;

FIG. 9 illustrates an example of generating medium access control (MAC)protocol data unit (PDU) according to an embodiment of the disclosure;

FIG. 10 illustrates another example of generating MAC PDU according toan embodiment of the disclosure;

FIG. 11 is a block diagram of a terminal according to an embodiment ofthe disclosure; and

FIG. 12 is a block diagram of a base station according to an embodimentof the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

It is known to those skilled in the art that blocks of a flowchart (orsequence diagram) and a combination of flowcharts may be represented andexecuted by computer program instructions. These computer programinstructions may be loaded on a processor of a general purpose computer,special purpose computer, or programmable data processing equipment.When the loaded program instructions are executed by the processor, theycreate a means for carrying out functions described in the flowchart.Because the computer program instructions may be stored in a computerreadable memory that is usable in a specialized computer or aprogrammable data processing equipment, it is also possible to createarticles of manufacture that carry out functions described in theflowchart. Because the computer program instructions may be loaded on acomputer or a programmable data processing equipment, when executed asprocesses, they may carry out operations of functions described in theflowchart.

A block of a flowchart may correspond to a module, a segment, or a codecontaining one or more executable instructions implementing one or morelogical functions, or may correspond to a part thereof. In some cases,functions described by blocks may be executed in an order different fromthe listed order. For example, two blocks listed in sequence may beexecuted at the same time or executed in reverse order.

In this description, the words “unit”, “module” or the like may refer toa software component or hardware component, such as, for example, afield-programmable gate array (FPGA) or an application-specificintegrated circuit (ASIC) capable of carrying out a function or anoperation. However, a “unit”, or the like, is not limited to hardware orsoftware. A unit, or the like, may be configured so as to reside in anaddressable storage medium or to drive one or more processors. Units, orthe like, may refer to software components, object-oriented softwarecomponents, class components, task components, processes, functions,attributes, procedures, subroutines, program code segments, drivers,firmware, microcode, circuits, data, databases, data structures, tables,arrays or variables. A function provided by a component and unit may bea combination of smaller components and units, and may be combined withothers to compose larger components and units. Components and units maybe configured to drive a device or one or more processors in a securemultimedia card.

Prior to the detailed description, terms or definitions necessary tounderstand the disclosure are described. However, these terms should beconstrued in a non-limiting way.

The “base station (BS)” is an entity communicating with a user equipment(UE) and may be referred to as BS, base transceiver station (BTS), nodeB (NB), evolved NB (eNB), access point (AP), 5G NB (5GNB), or nextgeneration node B (gNB).

The “UE” is an entity communicating with a BS and may be referred to asUE, device, mobile station (MS), mobile equipment (ME), or terminal.

In the recent years several broadband wireless technologies have beendeveloped to meet the growing number of broadband subscribers and toprovide more and better applications and services. The second generationwireless communication system has been developed to provide voiceservices while ensuring the mobility of users. Third generation wirelesscommunication system supports not only the voice service but also dataservice. In recent years, the fourth wireless communication system hasbeen developed to provide high-speed data service. However, currently,the 4G wireless communication system suffers from lack of resources tomeet the growing demand for high speed data services. So 5G wirelesscommunication system is being developed to meet the growing demand forhigh speed data services, support ultra-reliability and low latencyapplications.

The 5G wireless communication system will be implemented not only inlower frequency bands but also in higher frequency (mmWave) bands, e.g.,10 GHz to 100 GHz bands, so as to accomplish higher data rates. Tomitigate propagation loss of the radio waves and increase thetransmission distance, the beamforming, massive Multiple-InputMultiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are beingconsidered in the design of 5G wireless communication system. Inaddition, the 5G wireless communication system is expected to addressdifferent use cases having quite different requirements in terms of datarate, latency, reliability, mobility etc. However, it is expected thatthe design of the air-interface of the 5G wireless communication systemwould be flexible enough to serve the UEs having quite differentcapabilities depending on the use case and market segment the UE caterservice to the end customer. Few example use cases the 5G wirelesscommunication system wireless system is expected to address is enhancedMobile Broadband (eMBB), massive Machine Type Communication (m-MTC),ultra-reliable low latency communication (URLL) etc. The eMBBrequirements like tens of Gbps data rate, low latency, high mobility soon and so forth address the market segment representing the wirelessbroadband subscribers needing internet connectivity everywhere,according to the related art, all the time and on the go. The m-MTCrequirements like very high connection density, infrequent datatransmission, very long battery life, low mobility address so on and soforth address the market segment representing the Internet of Things(IoT)/Internet of Everything (IoE) envisioning connectivity of billionsof devices. The URLL requirements like very low latency, very highreliability and variable mobility so on and so forth address the marketsegment representing the Industrial automation application,vehicle-to-vehicle/vehicle-to-infrastructure communication foreseen asone of the enablers for autonomous cars.

In the 5G wireless communication system operating in higher frequency(mmWave) bands, UE and gNB communicates with each other usingBeamforming. Beamforming techniques are used to mitigate the propagationpath losses and to increase the propagation distance for communicationat higher frequency band. Beamforming enhances the transmission andreception performance using a high-gain antenna. Beamforming can beclassified into Transmission (TX) beamforming performed in atransmitting end and reception (RX) beamforming performed in a receivingend. In general, the TX beamforming increases directivity by allowing anarea in which propagation reaches to be densely located in a specificdirection by using a plurality of antennas.

In this situation, aggregation of the plurality of antennas can bereferred to as an antenna array, and each antenna included in the arraycan be referred to as an array element. The antenna array can beconfigured in various forms such as a linear array, a planar array, etc.The use of the TX beamforming results in the increase in the directivityof a signal, thereby increasing a propagation distance. Further, sincethe signal is almost not transmitted in a direction other than adirectivity direction, a signal interference acting on another receivingend is significantly decreased. The receiving end can performbeamforming on a RX signal by using a RX antenna array. The RXbeamforming increases the RX signal strength transmitted in a specificdirection by allowing propagation to be concentrated in a specificdirection, and excludes a signal transmitted in a direction other thanthe specific direction from the RX signal, thereby providing an effectof blocking an interference signal.

By using beamforming technique, a transmitter can make plurality oftransmit beam patterns of different directions. Each of these transmitbeam patterns can be also referred as TX beam. Wireless communicationsystem operating at high frequency uses plurality of narrow TX beams totransmit signals in the cell as each narrow TX beam provides coverage toa part of cell. The narrower the TX beam, higher is the antenna gain andhence the larger the propagation distance of signal transmitted usingbeamforming. A receiver can also make plurality of RX beam patterns ofdifferent directions. Each of these receive patterns can be alsoreferred as RX beam.

The 5G wireless communication system (also referred as next generationradio or NR), supports standalone mode of operation as well dualconnectivity (DC). In DC a multiple Rx/Tx UE may be configured toutilize resources provided by two different nodes (or NBs) connected vianon-ideal backhaul. One node acts as the Master Node (MN) and the otheras the Secondary Node (SN). The MN and SN are connected via a networkinterface and at least the MN is connected to the core network. NR alsosupports Multi-RAT Dual Connectivity (MR-DC) operation whereby a UE inradio resource control connected (RRC_CONNECTED) is configured toutilize radio resources provided by two distinct schedulers, located intwo different nodes connected via a non-ideal backhaul and providingeither E-UTRA (Evolved Universal Mobile Telecommunications System(UNITS) Terrestrial Radio Access) (i.e. if the node is an ng-eNB) or NRaccess (i.e. if the node is a gNB). In NR for a UE in RRC_CONNECTED notconfigured with carrier aggregation (CA)/DC there is only one servingcell comprising of the primary cell. For a UE in RRC_CONNECTEDconfigured with CA/DC the term ‘serving cells’ is used to denote the setof cells comprising of the Special Cell(s) and all secondary cells. InNR the term Master Cell Group (MCG) refers to a group of serving cellsassociated with the Master Node, comprising of the Primary Cell (PCell)and optionally one or more Secondary Cells (SCells). In NR the termSecondary Cell Group (SCG) refers to a group of serving cells associatedwith the Secondary Node, comprising of the Primary SCG Cell (PSCell) andoptionally one or more SCells. In NR PCell refers to a serving cell inMCG, operating on the primary frequency, in which the UE either performsthe initial connection establishment procedure or initiates theconnection re-establishment procedure. In NR for a UE configured withCA, SCell is a cell providing additional radio resources on top ofSpecial Cell. PSCell refers to a serving cell in SCG in which the UEperforms random access when performing the Reconfiguration with Syncprocedure. For Dual Connectivity operation the term SpCell (i.e. SpecialCell) refers to the PCell of the MCG or the PSCell of the SCG, otherwisethe term Special Cell refers to the PCell.

In the 5G wireless communication system (or NR), Physical DownlinkControl Channel (PDCCH) is used to schedule downlink (DL) transmissionson Physical Downlink Shared Channel (PDSCH) and uplink (UL)transmissions on Physical Uplink Shared Channel (PUSCH), where theDownlink Control Information (DCI) on PDCCH includes: Downlinkassignments containing at least modulation and coding format, resourceallocation, and hybrid automatic repeat request (HARQ) informationrelated to downlink shared channel (DL-SCH); Uplink scheduling grantscontaining at least modulation and coding format, resource allocation,and hybrid-ARQ information related to uplink shared channel (UL-SCH). Inaddition to scheduling, PDCCH can be used to for: Activation anddeactivation of configured PUSCH transmission with configured grant;Activation and deactivation of PDSCH semi-persistent transmission;Notifying one or more UEs of the slot format; Notifying one or more UEsof the physical resource block(s) (PRB(s)) and orthogonal frequencydivision multiplexing (OFDM) symbol(s) where the UE may assume notransmission is intended for the UE; Transmission of transmission powercontrol (TPC) commands for Physical Uplink Control Channel (PUCCH) andPUSCH; Transmission of one or more TPC commands for sounding referencesignal (SRS) transmissions by one or more UEs; Switching a UE's activebandwidth part; Initiating a random access procedure.

A UE monitors a set of PDCCH candidates in the configured monitoringoccasions in one or more configured COntrol REsource SETs (CORESETs)according to the corresponding search space configurations. A CORESETconsists of a set of PRBs with a time duration of 1 to 3 OFDM symbols.The resource units Resource Element Groups (REGs) and Control ChannelElements (CCEs) are defined within a CORESET with each CCE consisting aset of REGs. Control channels are formed by aggregation of CCE.Different code rates for the control channels are realized byaggregating different number of CCE. Interleaved and non-interleavedCCE-to-REG mapping are supported in a CORESET. Polar coding is used forPDCCH. Each resource element group carrying PDCCH carries its owndemodulation reference signal (DMRS). Quadrature phase shift keying(QPSK) modulation is used for PDCCH.

In NR, a list of search space configurations is signaled by gNB for eachconfigured bandwidth part (BWP) wherein each search configuration isuniquely identified by an identifier. Identifier of search spaceconfiguration to be used for specific purpose such as paging reception,system information (SI) reception, random access response (RAR)reception is explicitly signaled by gNB. In NR search spaceconfiguration comprises of parameters Monitoring-periodicity-PDCCH-slot,Monitoring-offset-PDCCH-slot, Monitoring-symbols-PDCCH-within-slot andduration. A UE determines PDCCH monitoring occasion (s) within a slotusing the parameters PDCCH monitoring periodicity(Monitoring-periodicity-PDCCH-slot), the PDCCH monitoring offset(Monitoring-offset-PDCCH-slot), and the PDCCH monitoring pattern(Monitoring-symbols-PDCCH-within-slot). PDCCH monitoring occasions arethere in slots ‘x’ to x+duration where the slot with number ‘x’ in aradio frame with number ‘y’ satisfies the Equation 1 below:(y*(number of slots in a radioframe)+x−Monitoring-offset-PDCCH-slot)mod(Monitoring-periodicity-PDCCH-slot)=0;  Equation1

The starting symbol of a PDCCH monitoring occasion in each slot havingPDCCH monitoring occasion is given byMonitoring-symbols-PDCCH-within-slot. The length (in symbols) of a PDCCHmonitoring occasion is given in the corset associated with the searchspace. search space configuration includes the identifier of CORESETconfiguration associated with it. A list of CORESET configurations aresignaled by gNB for each configured BWP wherein each CORESETconfiguration is uniquely identified by an identifier. Note that eachradio frame is of 10 ms duration. Radio frame is identified by a radioframe number or system frame number. Each radio frame comprises ofseveral slots wherein the number of slots in a radio frame and durationof slots depends on sub carrier spacing. The number of slots in a radioframe and duration of slots depends radio frame for each supportedsubcarrier spacing (SCS) is pre-defined in NR. Each CORESETconfiguration is associated with a list of TCI (Transmissionconfiguration indicator) states. One DL reference signal (RS) identifier(ID) (SSB or channel state information reference signal (CSI-RS)) isconfigured per TCI state. The list of TCI states corresponding to aCORESET configuration is signaled by gNB via RRC signaling. One of theTCI state in TCI state list is activated and indicated to UE by gNB. TCIstate indicates the DL TX beam (DL TX beam is quasi-collocated (QCLed)with SSB/CSI RS of TCI state) used by GNB for transmission of PDCCH inthe PDCCH monitoring occasions of a search space.

In NR bandwidth adaptation (BA) is supported. With BA, the receive andtransmit bandwidth of a UE need not be as large as the bandwidth of thecell and can be adjusted: the width can be ordered to change (e.g. toshrink during period of low activity to save power); the location canmove in the frequency domain (e.g. to increase scheduling flexibility);and the subcarrier spacing can be ordered to change (e.g. to allowdifferent services). A subset of the total cell bandwidth of a cell isreferred to as a Bandwidth Part (BWP).

BA is achieved by configuring RRC connected UE with BWP(s) and tellingthe UE which of the configured BWPs is currently the active one. When BAis configured, the UE only has to monitor PDCCH on the one active BWPi.e. it does not have to monitor PDCCH on the entire DL frequency of theserving cell. In RRC connected state, UE is configured with one or moreDL and UL BWPs, for each configured Serving Cell (i.e. PCell or SCell).For an activated Serving Cell, there is always one active UL and DL BWPat any point in time. The BWP switching for a Serving Cell is used toactivate an inactive BWP and deactivate an active BWP at a time. The BWPswitching is controlled by the PDCCH indicating a downlink assignment oran uplink grant, by the bwp-InactivityTimer, by RRC signaling, or by themedium access control (MAC) entity itself upon initiation of RandomAccess procedure. Upon addition of SpCell or activation of an SCell, theDL BWP and UL BWP indicated by firstActiveDownlinkBWP-Id andfirstActiveUplinkBWP-Id respectively is active without receiving PDCCHindicating a downlink assignment or an uplink grant. The active BWP fora Serving Cell is indicated by either RRC or PDCCH. For unpairedspectrum, a DL BWP is paired with a UL BWP, and BWP switching is commonfor both UL and DL. Upon expiry of BWP inactivity timer UE switch to theactive DL BWP to the default DL BWP or initial DL BWP (if default DL BWPis not configured).

In the 5G wireless communication system, random access (RA) issupported. Random access (RA) is used to achieve uplink (UL) timesynchronization. RA is used during initial access, handover, RRCconnection re-establishment procedure, scheduling request transmission,SCG addition/modification, beam failure recovery and data or controlinformation transmission in UL by non-synchronized UE in RRC CONNECTEDstate. Several types of random access procedure is supported.

Contention based random access (CBRA): This is also referred as 4 stepCBRA. In this type of random access, UE first transmits Random Accesspreamble (also referred as Msg1) and then waits for Random accessresponse (RAR) in the RAR window. RAR is also referred as Msg2. Nextgeneration node B (gNB) transmits the RAR on PDSCH. PDCCH scheduling thePDSCH carrying RAR is addressed to RA-radio network temporary identifier(RA-RNTI). RA-RNTI identifies the time-frequency resource (also referredas physical RA channel (PRACH) occasion or PRACH transmission (TX)occasion or RA channel (RACH) occasion) in which RA preamble wasdetected by gNB. The RA-RNTI is calculated as follows:RA-RNTI=1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id, where s_id isthe index of the first orthogonal frequency division multiplexing (OFDM)symbol of the PRACH occasion where UE has transmitted Msg1, i.e. RApreamble; 0≤s_id<14; t_id is the index of the first slot of the PRACHoccasion (0≤t_id<80); fid is the index of the PRACH occasion within theslot in the frequency domain (0≤f_id<8), and ul_carrier_id is the ULcarrier used for Msg1 transmission (0 for normal UL (NUL) carrier and 1for supplementary UL (SUL) carrier. Several RARs for various Randomaccess preambles detected by gNB can be multiplexed in the same RAR MACprotocol data unit (PDU) by gNB. An RAR in MAC PDU corresponds to UE'sRA preamble transmission if the RAR includes an RA preamble identifier(RAPID) of RA preamble transmitted by the UE. If the RAR correspondingto its RA preamble transmission is not received during the RAR windowand UE has not yet transmitted the RA preamble for a configurable(configured by gNB in RACH configuration) number of times, the UE goesback to first step i.e. select random access resource (preamble/RACHoccasion) and transmits the RA preamble. A backoff may be applied beforegoing back to first step.

If the RAR corresponding to its RA preamble transmission is received theUE transmits message 3 (Msg3) in UL grant received in RAR. Msg3 includesmessage such as RRC connection request, RRC connection re-establishmentrequest, RRC handover confirm, scheduling request, SI request etc. Itmay include the UE identity (i.e. cell-radio network temporaryidentifier (C-RNTI) or system architecture evolution (SAE)-temporarymobile subscriber identity (S-TMSI) or a random number). Aftertransmitting the Msg3, UE starts a contention resolution timer. Whilethe contention resolution timer is running, if UE receives a PDCCHaddressed to C-RNTI included in Msg3, contention resolution isconsidered successful, contention resolution timer is stopped and RAprocedure is completed. While the contention resolution timer isrunning, if UE receives contention resolution MAC control element (CE)including the UE's contention resolution identity (first X bits ofcommon control channel (CCCH) service data unit (SDU) transmitted inMsg3), contention resolution is considered successful, contentionresolution timer is stopped and RA procedure is completed. If thecontention resolution timer expires and UE has not yet transmitted theRA preamble for a configurable number of times, UE goes back to firststep i.e. select random access resource (preamble/RACH occasion) andtransmits the RA preamble. A backoff may be applied before going back tofirst step.

Contention free random access (CFRA): This is also referred as legacyCFRA or 4 step CFRA. CFRA procedure is used for scenarios such ashandover where low latency is required, timing advance establishment forSCell, etc. Evolved node B (eNB) assigns to UE dedicated Random accesspreamble. UE transmits the dedicated RA preamble. ENB transmits the RARon PDSCH addressed to RA-RNTI. RAR conveys RA preamble identifier andtiming alignment information. RAR may also include UL grant. RAR istransmitted in RAR window similar to CBRA procedure. CFRA is consideredsuccessfully completed after receiving the RAR including RAPID of RApreamble transmitted by the UE. In case RA is initiated for beam failurerecovery, CFRA is considered successfully completed if PDCCH addressedto C-RNTI is received in search space for beam failure recovery. If theRAR window expires and RA is not successfully completed and UE has notyet transmitted the RA preamble for a configurable (configured by gNB inRACH configuration) number of times, the UE retransmits the RA preamble.

For certain events such has handover and beam failure recovery ifdedicated preamble(s) are assigned to UE, during first step of randomaccess i.e. during random access resource selection for Msg1transmission UE determines whether to transmit dedicated preamble ornon-dedicated preamble. Dedicated preambles is typically provided for asubset of SSBs/CSI-RSs. If there is no SSB/CSI-RS having DL referencesignal received power (RSRP) above a threshold amongst the SSBs/CSI-RSsfor which contention free random access resources (i.e. dedicatedpreambles/ROs) are provided by gNB, UE select non-dedicated preamble.Otherwise UE select dedicated preamble. So, during the RA procedure, onerandom access attempt can be CFRA while other random access attempt canbe CBRA.

2 step contention based random access (2 step CBRA): In the first step,UE transmits random access preamble on PRACH and a payload (i.e. MACPDU) on PUSCH. The random access preamble and payload transmission isalso referred as MsgA. In the second step, after MsgA transmission, theUE monitors for a response from the network (i.e. gNB) within aconfigured window. The response is also referred as MsgB. If CCCH SDUwas transmitted in MsgA payload, UE performs contention resolution usingthe contention resolution information in MsgB. The contention resolutionis successful if the contention resolution identity received in MsgBmatches first 48 bits of CCCH SDU transmitted in MsgA. If C-RNTI wastransmitted in MsgA payload, the contention resolution is successful ifUE receives PDCCH addressed to C-RNTI. If contention resolution issuccessful, random access procedure is considered successfullycompleted. Instead of contention resolution information corresponding tothe transmitted MsgA, MsgB may include a fallback informationcorresponding to the random access preamble transmitted in MsgA. If thefallback information is received, UE transmits Msg3 and performscontention resolution using Msg4 as in CBRA procedure. If contentionresolution is successful, random access procedure is consideredsuccessfully completed. If contention resolution fails upon fallback(i.e. upon transmitting Msg3), UE retransmits MsgA. If configured windowin which UE monitor network response after transmitting MsgA expires andUE has not received MsgB including contention resolution information orfallback information as explained above, UE retransmits MsgA. If therandom access procedure is not successfully completed even aftertransmitting the MsgA configurable number of times, UE fallbacks to 4step RACH procedure i.e. UE only transmits the PRACH preamble.

MsgA payload may include one or more of CCCH SDU, dedicated controlchannel (DCCH) SDU, dedicated traffic channel (DTCH) SDU, buffer statusreport (BSR) MAC CE, power headroom report (PHR) MAC CE, SSBinformation, C-RNTI MAC CE, or padding. MsgA may include UE ID (e.g.random ID, S-TMSI, C-RNTI, resume ID, etc.) along with preamble in firststep. The UE ID may be included in the MAC PDU of the MsgA. UE ID suchas C-RNTI may be carried in MAC CE wherein MAC CE is included in MACPDU. Other UE IDs (such random ID, S-TMSI, C-RNTI, resume ID, etc.) maybe carried in CCCH SDU. The UE ID can be one of random ID, S-TMSI,C-RNTI, resume ID, IMSI, idle mode ID, inactive mode ID, etc. The UE IDcan be different in different scenarios in which UE performs the RAprocedure. When UE performs RA after power on (before it is attached tothe network), then UE ID is the random ID. When UE perform RA in IDLEstate after it is attached to network, the UE ID is S-TMSI. If UE has anassigned C-RNTI (e.g. in connected state), the UE ID is C-RNTI. In caseUE is in INACTIVE state, UE ID is resume ID. In addition to UE ID, someaddition ctrl information can be sent in MsgA. The control informationmay be included in the MAC PDU of the MsgA. The control information mayinclude one or more of connection request indication, connection resumerequest indication, SI request indication, buffer status indication,beam information (e.g. one or more DL TX beam ID(s) or SSB ID(s)), beamfailure recovery indication/information, data indicator, cell/BS/TRPswitching indication, connection re-establishment indication,reconfiguration complete or handover complete message, etc.

2 step contention free random access (2 step CFRA): In this case gNBassigns to UE dedicated Random access preamble(s) and PUSCH resource(s)for MsgA transmission. RO(s) to be used for preamble transmission mayalso be indicated. In the first step, UE transmits random accesspreamble on PRACH and a payload on PUSCH using the contention freerandom access resources (i.e. dedicated preamble/PUSCH resource/RO). Inthe second step, after MsgA transmission, the UE monitors for a responsefrom the network (i.e. gNB) within a configured window. If UE receivesPDCCH addressed to C-RNTI, random access procedure is consideredsuccessfully completed. If UE receives fallback informationcorresponding to its transmitted preamble, random access procedure isconsidered successfully completed.

For certain events such has handover and beam failure recovery ifdedicated preamble(s) and PUSCH resource(s) are assigned to UE, duringfirst step of random access i.e. during random access resource selectionfor MsgA transmission UE determines whether to transmit dedicatedpreamble or non-dedicated preamble. Dedicated preambles are typicallyprovided for a subset of SSBs/CSI-RSs. If there is no SSB/CSI-RS havingDL RSRP above a threshold amongst the SSBs/CSI-RSs for which contentionfree random access resources (i.e. dedicated preambles/ROs/PUSCHresources) are provided by gNB, UE select non dedicated preamble.Otherwise UE select dedicated preamble. So, during the RA procedure, onerandom access attempt can be 2 step CFRA while other random accessattempt can be 2 step CBRA.

Upon initiation of random access procedure, UE first selects the carrier(SUL or NUL). If the carrier to use for the Random Access procedure isexplicitly signaled by gNB, UE select the signaled carrier forperforming Random Access procedure. If the carrier to use for the RandomAccess procedure is not explicitly signaled by gNB; and if the ServingCell for the Random Access procedure is configured with supplementaryuplink and if the RSRP of the downlink pathloss reference is less thanrsrp-ThresholdSSB-SUL: UE select the SUL carrier for performing RandomAccess procedure. Otherwise, UE select the NUL carrier for performingRandom Access procedure. Upon selecting the UL carrier, UE determinesthe UL and DL BWP for random access procedure. UE then determineswhether to perform 2 step or 4 step RACH for this random accessprocedure.

-   -   If this random access procedure is initiated by PDCCH order and        if the ra-PreambleIndex explicitly provided by PDCCH is not        0b000000, UE selects 4 step RACH.    -   else if 2 step contention free random access resources are        signaled by gNB for this random access procedure, UE selects 2        step RACH.    -   else if 4 step contention free random access resources are        signaled by gNB for this random access procedure, UE selects 4        step RACH.    -   else if the UL BWP selected for this random access procedure is        configured with only 2 step RACH resources, UE selects 2 step        RACH.    -   else if the UL BWP selected for this random access procedure is        configured with only 4 step RACH resources, UE selects 4 step        RACH.    -   else if the UL BWP selected for this random access procedure is        configured with both 2 step and 4 step RACH resources,    -   if RSRP of the downlink pathloss reference is below a configured        threshold, UE selects 4 step RACH. Otherwise UE selects 2 step        RACH.

In the 5G wireless communication system, node B (gNB) or base station incell broadcast Synchronization Signal and PBCH block (SSB) consists ofprimary and secondary synchronization signals (PSS, SSS) and systeminformation. System information includes common parameters needed tocommunicate in cell. In the 5G wireless communication system (alsoreferred as next generation radio or NR), System Information (SI) isdivided into the master information block (MIB) and a number of systeminformation blocks (SIBs) where:

-   -   the MIB is always transmitted on the BCH with a periodicity of        80 ms and repetitions made within 80 ms and it includes        parameters that are needed to acquire SIB1 from the cell.    -   the SIB1 is transmitted on the DL-SCH with a periodicity of 160        ms and variable transmission repetition. The default        transmission repetition periodicity of SIB1 is 20 ms but the        actual transmission repetition periodicity is up to network        implementation. The scheduling information in SIB 1 includes        mapping between SIBs and SI messages, periodicity of each SI        message and SI window length. The scheduling information in SIB        1 includes an indicator for each SI message, which indicates        whether the concerned SI message is being broadcasted or not. If        at least one SI message is not being broadcasted, SIB1 may        include random access resources (PRACH preamble(s) and PRACH        resource(s)) for requesting gNB to broadcast one or more SI        message(s).    -   SIBs other than SIB1 are carried in SystemInformation (SI)        messages, which are transmitted on the DL-SCH. Only SIBs having        the same periodicity can be mapped to the same SI message. Each        SI message is transmitted within periodically occurring time        domain windows (referred to as SI-windows with same length for        all SI messages). Each SI message is associated with a SI-window        and the SI-windows of different SI messages do not overlap. That        is, within one SI-window only the corresponding SI message is        transmitted. Any SIB except SIB1 can be configured to be cell        specific or area specific, using an indication in SIB1. The cell        specific SIB is applicable only within a cell that provides the        SIB while the area specific SIB is applicable within an area        referred to as SI area, which consists of one or several cells        and is identified by systemInformationAreaID.

In the 5G wireless communication system, RRC can be in one of thefollowing states: RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED. A UE iseither in RRC_CONNECTED state or in RRC_INACTIVE state when an RRCconnection has been established. If this is not the case, i.e. no RRCconnection is established, the UE is in RRC_IDLE state. The RRC statescan further be characterized as follows:

In the RRC_IDLE, a UE specific discontinuous (DRX) may be configured byupper layers. The UE monitors Short Messages transmitted with pagingRNTI (P-RNTI) over DCI; monitors a Paging channel for CN paging using5G-S-temporary mobile subscriber identity (5G-S-TMSI); performsneighboring cell measurements and cell (re-)selection; acquires systeminformation and can send SI request (if configured); performs logging ofavailable measurements together with location and time for loggedmeasurement configured UEs.

In RRC_INACTIVE, a UE specific DRX may be configured by upper layers orby RRC layer; UE stores the UE Inactive AS context; a RAN-basednotification area is configured by RRC layer. The UE monitors ShortMessages transmitted with P-RNTI over DCI; monitors a Paging channel forCN paging using 5G-S-TMSI and RAN paging using full I-RNTI; performsneighboring cell measurements and cell (re-)selection; performsRAN-based notification area updates periodically and when moving outsidethe configured RAN-based notification area; acquires system informationand can send SI request (if configured); performs logging of availablemeasurements together with location and time for logged measurementconfigured UEs.

In the RRC_CONNECTED, the UE stores the AS context and transfer ofunicast data to/from UE takes place. The UE monitors Short Messagestransmitted with P-RNTI over DCI, if configured; monitors controlchannels associated with the shared data channel to determine if data isscheduled for it; provides channel quality and feedback information;performs neighboring cell measurements and measurement reporting;acquires system information.

In the RRC_CONNECTED, network may initiate suspension of the RRCconnection by sending RRCRelease with suspend configuration. When theRRC connection is suspended, the UE stores the UE Inactive AS contextand any configuration received from the network, and transits toRRC_INACTIVE state. If the UE is configured with SCG, the UE releasesthe SCG configuration upon initiating a RRC Connection Resume procedure.The RRC message to suspend the RRC connection is integrity protected andciphered.

The resumption of a suspended RRC connection is initiated by upperlayers when the UE needs to transit from RRC_INACTIVE state toRRC_CONNECTED state or by RRC layer to perform a RAN based notificationarea (RNA) update or by RAN paging from NG-RAN. When the RRC connectionis resumed, network configures the UE according to the RRC connectionresume procedure based on the stored UE Inactive AS context and any RRCconfiguration received from the network. The RRC connection resumeprocedure re-activates AS security and re-establishes signaling radiobearer(s) (SRB(s)) and data radio bearer(s) (DRB(s)). In response to arequest to resume the RRC connection, the network may resume thesuspended RRC connection and send UE to RRC_CONNECTED, or reject therequest to resume and send UE to RRC_INACTIVE (with a wait timer), ordirectly re-suspend the RRC connection and send UE to RRC_INACTIVE, ordirectly release the RRC connection and send UE to RRC_IDLE, or instructthe UE to initiate NAS level recovery (in this case the network sends anRRC setup message).

Upon initiating the resume procedure, UE:

-   -   apply the default L1 parameter values as specified in        corresponding physical layer specifications, except for the        parameters for which values are provided in SIB1;    -   apply the default MAC Cell Group configuration    -   apply the CCCH configuration    -   start timer T319;    -   apply the timeAlignmentTimerCommon included in SIB1    -   apply the default SRB1 configuration    -   set the variable pending RNA-Update to false;    -   initiate transmission of the RRCResumeRequest message or        RRCResumeRequest1    -   restore the RRC configuration, RoHC state, the stored QoS flow        to DRB mapping rules and the KgNB and K_(RRCint) keys from the        stored UE Inactive AS context except for the following:        -   masterCellGroup;        -   mrdc-SecondaryCellGroup, if stored; and        -   pdcp-Config;    -   set the resumeMAC-I to the 16 least significant bits of the        MAC-I calculated:        -   with the K_(RRCint) key in the UE Inactive AS Context and            the previously configured integrity protection algorithm;            and        -   with all input bits for COUNT, BEARER and DIRECTION set to            binary ones;    -   derive the KgNB key based on the current KgNB key or the NH,        using the stored nextHopChainingCount value;    -   derive the K_(RRCenc) key, the K_(RRCint) key, the K_(UPint) key        and the K_(UPenc) key;    -   configure lower layers to apply integrity protection for all        signaling radio bearers except SRB0 using the configured        algorithm and the K_(RRCint) key and K_(UPint) key, i.e.,        integrity protection shall be applied to all subsequent messages        received and sent by the UE;    -   configure lower layers to apply ciphering for all signaling        radio bearers except SRB0 and to apply the configured ciphering        algorithm, the K_(RRCenc) key and the K_(UPenc) key derived,        i.e. the ciphering configuration shall be applied to all        subsequent messages received and sent by the UE;    -   re-establish PDCP entities for SRB1;    -   resume SRB1;    -   transmit RRCResumeRequest or RRCResumeRequest1.

In 5G wireless communication system, small data transmission (SDT) inRRC_INACTIVE is supported. The uplink data can be transmitted in Msg3 in4 step RA procedure, and can be transmitted in MsgA in 2 step RAprocedure. FIG. 1 is an example signaling flow for small datatransmission using 4 step RA.

FIG. 1 illustrates an example of small data transmission according to anembodiment of the disclosure.

Referring to FIG. 1 , criteria to initiate 4 step RA for SDT is met. UEselect preamble/RO from preambles/ROs for SDT. UE transmits randomaccess preamble and receives RAR including UL grant for Msg3transmission (110, 120).

The UE sends an RRCResumeRequest/RRCResumeRequest1 to the gNB (same asthe last serving GNB) on SRB 0 (130). It includes full/short I-RNTI(resumeIdentity), the resume cause (resumeCause), and an authenticationtoken (resumeMAC-I). The I-RNTI (short or full I-RNTI) is used forcontext identification and its value shall be the same as the I-RNTIthat the UE had received from the last serving gNB in the RRCReleasewith suspendConfig message. The ResumeMAC-I is a 16-bit messageauthentication token, the UE shall calculate it using the integrityalgorithm (NIA (NR integrity algorithm) or EIA (EPS integrityalgorithm)) in the stored AS security context, which was negotiatedbetween the UE and the last serving gNB and the K_(RRCint) from thestored AS security context with the following inputs:

-   -   KEY: it shall be set to current K_(RRCint);    -   BEARER: all its bits shall be set to 1.    -   DIRECTION: its bit shall be set to 1;    -   COUNT: all its bits shall be set to 1;    -   MESSAGE: it shall be set to VarResumeMAC-Input with following        inputs:        -   source physical cell identity (PCI) (set to the physical            cell identity of the PCell the UE was connected to prior to            suspension of the RRC connection)        -   target Cell-ID (Set to the cellIdentity of the first            PLMN-Identity included in the PLMN-IdentityInfoList            broadcasted in SIB1 of the target cell i.e. the cell to            which the UE is sending small data)        -   source C-RNTI (Set to C-RNTI that the UE had in the PCell it            was connected to prior to suspension of the RRC connection).

The UE resumes SRB(s) and DRB(s), derives new security keys using theNextHopChainingCount provided in the RRCRelease message of the previousRRC connection and re-establishes the AS security. The user data areciphered and integrity protected (Only for DRBs configured with UPintegrity protection) and transmitted on DTCH multiplexed with theRRCResumeRequest/RRCResumeRequest1 message on CCCH/CCCH1.

The gNB validates the resumeMAC-I and delivers the uplink data to UPF(140).

The gNB sends the RRCRelease message to keep the UE in RRC_INACTIVE.PDCCH is addressed to temporary C-RNTI (TC-RNTI). If downlink data isavailable, they are sent ciphered and integrity protected (Only for DRBsconfigured with UP integrity protection) on DTCH multiplexed with theRRCRelease message on DCCH (150, 160).

FIG. 2 shows the signaling flow for small data transmission using 2 stepRA. FIG. 2 illustrates another example of small data transmissionaccording to an embodiment of the disclosure.

Referring to FIG. 2 , criteria to initiate 2 step RA for SDT is met. UEselect preamble/RO/PO from preambles/ROs/POs for SDT. UE transmitsrandom access preamble (210).

In the MsgA payload, the UE sends an RRCResumeRequest/RRCResumeRequest1to the gNB (same as the last serving GNB) on SRB 0 (220). It includesfull/short I-RNTI (resumeIdentity), the resume cause (resumeCause), andan authentication token (resumeMAC-I). The I-RNTI (short or full I-RNTI)is used for context identification and its value shall be the same asthe I-RNTI that the UE had received from the last serving gNB in theRRCRelease with suspendConfig message. The ResumeMAC-I is a 16-bitmessage authentication token, the UE shall calculate it using theintegrity algorithm (MA or EIA) in the stored AS security context, whichwas negotiated between the UE and the last serving gNB and theK_(RRCint) from the stored AS security context with the followinginputs:

-   -   KEY: it shall be set to current K_(RRCint);    -   BEARER: all its bits shall be set to 1.    -   DIRECTION: its bit shall be set to 1;    -   COUNT: all its bits shall be set to 1;    -   MESSAGE: it shall be set to VarResumeMAC-Input with following        inputs:        -   source PCI (set to the physical cell identity of the PCell            the UE was connected to prior to suspension of the RRC            connection)        -   target Cell-ID (Set to the cellIdentity of the first            PLMN-Identity included in the PLMN-IdentityInfoList            broadcasted in SIB1 of the target cell i.e. the cell to            which the UE is sending small data)        -   source C-RNTI (Set to C-RNTI that the UE had in the PCell it            was connected to prior to suspension of the RRC connection).

The UE resumes all SRBs and DRBs, derives new security keys using theNextHopChainingCount provided in the RRCRelease message of the previousRRC connection and re-establishes the AS security. The user data areciphered and integrity protected (Only for DRBs configured with UPintegrity protection) and transmitted on DTCH multiplexed with theRRCResumeRequest/RRCResumeRequest1 message on CCCH/CCCH1.

The gNB validates the resumeMAC-I and delivers the uplink data to UPF(230).

3. The gNB sends the RRCRelease message to keep the UE in RRC_INACTIVEin MsgB along with successRAR. PDCCH is addressed to C-RNTI. If downlinkdata is available, they are sent ciphered and integrity protected (Onlyfor DRBs configured with UP integrity protection) on DTCH multiplexedwith the RRCRelease message on DCCH (240, 250).

FIG. 3 shows the signaling flow for small data transmission usingpreconfigured PUSCH resource. FIG. 3 illustrates another example ofsmall data transmission according to an embodiment of the disclosure.

Criteria to initiate SDT using preconfigured PUSCH resources is met.

Referring to FIG. 3 , in the preconfigured PUSCH resource, the UE sendsan RRCResumeRequest/RRCResumeRequest1 to the gNB (same as the lastserving GNB) on SRB 0 (310). It includes full/short I-RNTI(resumeIdentity), the resume cause (resumeCause), and an authenticationtoken (resumeMAC-I). The I-RNTI (short or full I-RNTI) is used forcontext identification and its value shall be the same as the I-RNTIthat the UE had received from the last serving gNB in the RRCReleasewith suspendConfig message. The ResumeMAC-I is a 16-bit messageauthentication token, the UE shall calculate it using the integrityalgorithm (MA or EIA) in the stored AS security context, which wasnegotiated between the UE and the last serving gNB and the K_(RRCint)from the stored AS security context with the following inputs:

-   -   KEY: it shall be set to current K_(RRCint);    -   BEARER: all its bits shall be set to 1.    -   DIRECTION: its bit shall be set to 1;    -   COUNT: all its bits shall be set to 1;    -   MESSAGE: it shall be set to VarResumeMAC-Input with following        inputs:        -   source PCI (set to the physical cell identity of the PCell            the UE was connected to prior to suspension of the RRC            connection)        -   target Cell-ID (Set to the cellIdentity of the first            PLMN-Identity included in the PLMN-IdentityInfoList            broadcasted in SIB1 of the target cell i.e. the cell to            which the UE is sending small data)        -   source C-RNTI (Set to C-RNTI that the UE had in the PCell it            was connected to prior to suspension of the RRC connection).

The UE resumes all SRBs and DRBs, derives new security keys using theNextHopChainingCount provided in the RRCRelease message of the previousRRC connection and re-establishes the AS security. The user data areciphered and integrity protected (Only for DRBs configured with UPintegrity protection) and transmitted on DTCH multiplexed with theRRCResumeRequest/RRCResumeRequest1 message on CCCH.

The UE can alternately transmit its small data by using one of thefollowing options:

-   -   RRCResumeRequest (or new RRC message). resumeIdentity,        ResumeMAC-I, resumeCause, NAS container in        RRCResumeRequest/RRCResumeRequest1. NAS container includes UL        data.    -   new MAC CE (resumeIdentity, ResumeMAC-I)+uplink data (on DTCH).        resumeIdentity is provided for UE identification purpose.        ResumeMAC-I is for security

The gNB validates the resumeMAC-I and delivers the uplink data to UPF(320).

The gNB sends the RRCRelease message to keep the UE in RRC_INACTIVE. ThePDCCH is addressed to C-RNTI. The C-RNTI is the one which the UE used incell from which it received preconfigured PUSCH resources. Alternately,the C-RNTI can be assigned along with preconfigured PUSCH resources. Ifdownlink data is available, they are sent ciphered and integrityprotected (Only for DRBs configured with UP integrity protection) onDTCH multiplexed with the RRCRelease message on DCCH (330, 340).

(Alternate 1) We can consider an alternate signaling flow wherein gNBcan schedule UL grant (PDCCH addressed to C-RNTI) before RRCRelease. Inthe UL transmission UE can indicate if it has more data to transmit. IfUE has more data to transmit, gNB can schedule UL grant. OtherwiseRRCRelease is transmitted. In the UL transmission, UE can also includeSSB ID(s) of SSB above threshold if the SSB indicated by PRACH preambleis no longer suitable.

(Alternate 2) Alternately, the gNB can transmit PDCCH addressed to RNTI(i.e. RNTI is the one assigned by gNB along with preconfigured resource,it can be assigned to other UEs as well) and scheduled DL transportblock (TB) includes contention resolution identity (it is first X bits(e.g. 48 bits) of resume message) and C-RNTI. If it matches with UE'scontention resolution identity, UE stops the monitoring timer and UE canconsider small data transmission as successful.

In the response of the small data transmission, UE can receive a signal(RRC message or DCI) for the following purpose: releasing pre-configuredPUSCH or switching to resume procedure (i.e. RRC_CONNECTED).

FIG. 4 illustrates an architecture supporting PC5 interface according toan embodiment of the disclosure.

Referring to FIG. 4 , 4G and 5G wireless communication system supportsvehicular communication services. Vehicular communication services,represented by Vehicle-to-Everything (V2X) services, can consist of thefollowing four different types: Vehicle-to-Vehicle (V2V),Vehicle-to-Infrastructure (V2I), Vehicle-to-Network (V2N) andVehicle-to-Pedestrian (V2P). In 5G (also referred as NR or New Radio)wireless communication system, V2X communication is being enhanced tosupport enhanced V2X use cases, which are broadly arranged into four usecase groups:

1) Vehicles Platooning enables the vehicles to dynamically form aplatoon travelling together. All the vehicles in the platoon obtaininformation from the leading vehicle to manage this platoon. Thisinformation allows the vehicles to drive closer than normal in acoordinated manner, going to the same direction and travelling together.

2) Extended Sensors enables the exchange of raw or processed datagathered through local sensors or live video images among vehicles, roadsite units, devices of pedestrian and V2X application servers. Thevehicles can increase the perception of their environment beyond of whattheir own sensors can detect and have a broader and holistic view of thelocal situation. High data rate is one of the key characteristics.

3) Advanced Driving enables semi-automated or full-automated driving.Each vehicle and/or Road Side Unit (RSU) shares its own perception dataobtained from its local sensors with vehicles in proximity and thatallows vehicles to synchronize and coordinate their trajectories ormaneuvers. Each vehicle shares its driving intention with vehicles inproximity too.

4) Remote Driving enables a remote driver or a V2X application tooperate a remote vehicle for those passengers who cannot drive bythemselves or remote vehicles located in dangerous environments. For acase where variation is limited and routes are predictable, such aspublic transportation, driving based on cloud computing can be used.High reliability and low latency are the main requirements.

V2X services can be provided by PC5 interface and/or Uu interface.Support of V2X services via PC5 interface is provided by NR sidelink(SL) communication or V2X sidelink communication, which is a mode ofcommunication whereby UEs can communicate with each other directly overthe PC5 interface using NR technology or EUTRA technology respectivelywithout traversing any network node. This communication mode issupported when the UE is served by RAN and when the UE is outside of RANcoverage. Only the UEs authorized to be used for V2X services canperform NR or V2X sidelink communication. The NG-RAN architecturesupports the PC5 interface as illustrated in FIG. 4 . Sidelinktransmission and reception over the PC5 interface are supported when theUE is inside NG-RAN coverage, irrespective of which RRC state the UE isin, and when the UE is outside NG-RAN coverage. Support of V2X servicesvia the PC5 interface can be provided by NR Sidelink Communicationand/or V2X Sidelink Communication. NR Sidelink Communication may be usedto support other services than V2X services.

NR or V2X Sidelink Communication can support three types of transmissionmodes.

-   -   Unicast transmission, characterized by support of at least one        PC5-RRC connection between peer UEs; Transmission and reception        of control information and user traffic between peer UEs in        sidelink; Support of sidelink HARQ feedback; Support of radio        link control (RLC) acknowledged mode (AM); and Support of        sidelink radio link monitoring (RLM) for both peer UEs to detect        radio link failure (RLF).    -   Groupcast transmission, characterized by: Transmission and        reception of user traffic among UEs belonging to a group in        sidelink; Support of sidelink HARQ feedback.    -   Broadcast transmission, characterized by: Transmission and        reception of user traffic among UEs in sidelink.

The AS protocol stack for the control plane in the PC5 interfaceconsists of RRC, packet data convergence protocol (PDCP), RLC and MACsublayer, and the physical layer. The AS protocol stack for user planein the PC5 interface consists of SDAP, PDCP, RLC and MAC sublayer, andthe physical layer. Sidelink Radio bearers (SLRB) are categorized intotwo groups: sidelink data radio bearers (SL DRB) for user plane data andsidelink signaling radio bearers (SL SRB) for control plane data.Separate SL SRBs using different sidelink control channels (SCCHs) areconfigured for PC5-RRC and PC5-S signaling respectively.

The MAC sublayer provides the following services and functions over thePC5 interface: Radio resource selection; Packet filtering; Priorityhandling between uplink and sidelink transmissions for a given UE;Sidelink CSI reporting. With logical channel prioritization (LCP)restrictions in MAC, only sidelink logical channels belonging to thesame destination can be multiplexed into a MAC PDU for every unicast,groupcast and broadcast transmission which is associated to thedestination. NG-RAN can also control whether a sidelink logical channelcan utilize the resources allocated to a configured sidelink grantType 1. For packet filtering, a sidelink shared channel (SL-SCH) MACheader including portions of both Source Layer-2 ID and a DestinationLayer-2 ID is added to each MAC PDU. LCID included within a MACsubheader uniquely identifies a logical channel within the scope of theSource Layer-2 ID and Destination Layer-2 ID combination. The followinglogical channels are used in sidelink:

-   -   Sidelink Control Channel (SCCH): a sidelink channel for        transmitting control information from one UE to other UE(s);    -   Sidelink Traffic Channel (STCH): a sidelink channel for        transmitting user information from one UE to other UE(s);    -   Sidelink Broadcast Control Channel (SBCCH): a sidelink channel        for broadcasting sidelink system information from one UE to        other UE(s).

The following connections between logical channels and transportchannels exist:

-   -   SCCH can be mapped to SL-SCH;    -   STCH can be mapped to SL-SCH;    -   SBCCH can be mapped to SL-BCH.

The RRC sublayer provides the following services and functions over thePC5 interface:

-   -   Transfer of a PC5-RRC message between peer UEs;    -   Maintenance and release of a PC5-RRC connection between two UEs;    -   Detection of sidelink radio link failure for a PC5-RRC        connection.

A PC5-RRC connection is a logical connection between two UEs for a pairof Source and Destination Layer-2 IDs which is considered to beestablished after a corresponding PC5 unicast link is established. Thereis one-to-one correspondence between the PC5-RRC connection and the PC5unicast link. A UE may have multiple PC5-RRC connections with one ormore UEs for different pairs of Source and Destination Layer-2 IDs.Separate PC5-RRC procedures and messages are used for a UE to transferUE capability and sidelink configuration including SLRB configuration tothe peer UE. Both peer UEs can exchange their own UE capability andsidelink configuration using separate bi-directional procedures in bothsidelink directions. If it is not interested in sidelink transmission,if sidelink RLF on the PC5-RRC connection is declared, or if the Layer-2link release procedure is completed, UE releases the PC5-RRC connection.

The UE can operate in two modes for resource allocation in sidelink:

-   -   Scheduled resource allocation, characterized by:        -   The UE needs to be RRC_CONNECTED in order to transmit data;        -   NG-RAN schedules transmission resources.    -   UE autonomous resource selection, characterized by:        -   The UE can transmit data when inside NG-RAN coverage,            irrespective of which RRC state the UE is in, and when            outside NG-RAN coverage;        -   The UE autonomously selects transmission resources from a            pool of resources.

For NR sidelink communication, the UE performs sidelink transmissionsonly on a single carrier.

The two modes for resource allocation are described in detail as below.

Scheduled Resource Allocation: NG-RAN can dynamically allocate resourcesto the UE via the sidelink RNTI (SL-RNTI) on PDCCH(s) for NR sidelinkCommunication. In addition, NG-RAN can allocate sidelink resources to UEwith two types of configured sidelink grants:

-   -   With type 1, RRC directly provides the configured sidelink grant        for NR sidelink communication    -   With type 2, RRC provides the periodicity of the configured        sidelink grant while PDCCH can either signal and activate the        configured sidelink grant, or deactivate it. The PDCCH provides        the actual grant (i.e. resources) to be used. The PDCCH is        addressed to SL-CS-RNTI for NR sidelink communication and SL        Semi-Persistent Scheduling V-RNTI for V2X sidelink        communication.

For the UE performing NR sidelink communication, there can be more thanone configured sidelink grant activated at a time on the carrierconfigured for sidelink transmission. When beam failure or physicallayer problem occurs on NR Uu, the UE can continue using the configuredsidelink grant Type 1. During handover, the UE can be provided withconfigured sidelink grants via handover command, regardless of the type.If provided, the UE activates the configured sidelink grant Type 1 uponreception of the handover command. The UE can send sidelink bufferstatus report to support scheduler operation in NG-RAN. The sidelinkbuffer status reports refer to the data that is buffered in for a groupof logical channels (or, logical channel group (LCG) per destination inthe UE. Eight LCGs are used for reporting of the sidelink buffer statusreports. Two formats, which are SL BSR and truncated SL BSR, are used.

UE Autonomous Resource Allocation: The UE autonomously selects sidelinkgrant from a pool of resources provided by broadcast system informationor dedicated signaling while inside NG-RAN coverage or bypreconfiguration while outside NG-RAN coverage.

For NR sidelink communication, the pools of resources can be providedfor a given validity area where the UE does not need to acquire a newpool of resources while moving within the validity area, at least whenthis pool is provided by SIB (e.g. reuse valid area of NR SIB). NR SIBvalidity mechanism is reused to enable validity area for SL resourcepool configured via broadcasted system information. The UE is allowed totemporarily use UE autonomous resource selection with random selectionfor sidelink transmission based on configuration of the exceptionaltransmission resource pool.

For V2X sidelink transmission, during handover, transmission resourcepool configurations including exceptional transmission resource pool forthe target cell can be signaled in the handover command to reduce thetransmission interruption. In this way, the UE may use the V2X sidelinktransmission resource pools of the target cell before the handover iscompleted as long as either synchronization is performed with the targetcell in case eNB is configured as synchronization source orsynchronization is performed with Global Navigation Satellite System(GNSS) in case GNSS is configured as synchronization source. If theexceptional transmission resource pool is included in the handovercommand, the UE uses randomly selected resources from the exceptionaltransmission resource pool, starting from the reception of handovercommand. If the UE is configured with scheduled resource allocation inthe handover command, the UE continues to use the exceptionaltransmission resource pool while the timer associated with handover isrunning. If the UE is configured with autonomous resource selection inthe target cell the UE continues to use the exceptional transmissionresource pool until the sensing results on the transmission resourcepools for autonomous resource selection are available. For exceptionalcases (e.g. during RLF, during transition from RRC IDLE to RRC CONNECTEDor during change of dedicated V2X sidelink resource pools within acell), the UE may select resources in the exceptional pool provided inserving cell's SIB21 or in dedicated signaling based on randomselection, and uses them temporarily. During cell reselection, theRRC_IDLE UE may use the randomly selected resources from the exceptionaltransmission resource pool of the reselected cell until the sensingresults on the transmission resource pools for autonomous resourceselection are available.

In NR, dual active protocol stack (DAPS) handover (HO) is supportedwherein the UE can communicate with source PCell and Target Cellconcurrently. In case of DAPS HO, two MAC entities exist concurrentlyfor MCG. During the DAPS HO Existing MAC entity of MCG is not reset andNew MAC entity of MCG is created. Existing MAC entity (referred asSource MCG MAC entity), handles DL/UL of DAPS bearer during HO andhandles UL of DAPS bearer until source is released after HO. New MACentity (referred as Target MCG MAC entity), handles DL/UL of SRBs duringHO and after HO, it handles DL/UL of SRBs/DRBs. Here, embodiment ofperforming SL MAC operation using two MAC entities is described indetail.

Embodiment 1—SL Communication Handling

FIGS. 5A and 5B illustrate an example of a sidelink (SL) communicationhandling according to various embodiment of the disclosure.

1. UE is in RRC_CONNECTED state. There are MAC entities for each CGs(MCG and SCG) which perform the MAC operation for the respective CGs(505). Note that if SCG is not configured, there will be only one MACentity i.e. MAC entity for MCG.

2. UE receives the first RRCReconfiguration message from gNB where themessage includes sl-ConfigDedicatedNR IE (510). sl-ConfigDedicatedNR IEincludes the dedicated SL communication parameters/configuration.

3. UE applies the MAC parameters included in sl-ConfigDedicatedNR ofreceived first message to the MCG MAC entity. MAC performs operationrelated to SL communication according to the configured parameters(515).

4. UE receives 2nd RRCReconfiguration message where the message includesReconfigurationWithSync IE for MCG and sl-ConfigDedicatedNR IE (520).

5. Upon receiving the second message, UE checks if there is at least oneDAPS bearer in radio bearer configuration in received 2nd message (525).

6. if there is no DAPS bearer in radio bearer configuration in receivedsecond message (525), UE perform the following operation:

-   -   Start the timer T304 (530).    -   Reset the MCG MAC entity (535). Operations for MAC reset are        described later.    -   Apply the mac-CellGroupConfig of MCG received in the 2nd message        to MCG MAC entity (540).    -   Apply the MAC parameters included in sl-ConfigDedicatedNR of        received 2nd message to the MCG MAC entity. MCG MAC entity        performs operation related to SL communication according to the        configured parameters (545).    -   Release sl-ConfigDedicatedNR received in first message (550).    -   Initiate random access towards the target SpCell.    -   If T304 expires: initiate RRC Connection Re-establishment        wherein the MCG MAC entity is reset and MCG MAC configuration is        released (555).

7. if there is at least one DAPS bearer in radio bearer configuration inreceived second message (525), UE perform the following operation:

-   -   Start the timer T304 (560).    -   Create a new MCG MAC entity (‘referred as target MCG MAC        entity’). The existing MAC entity is referred as source MCG MAC        entity (565).    -   Perform partial reset of source MCG MAC entity (570). Source MCG        MAC entity operation related to SL communication is stopped.        Operation for partial MAC reset are described later.    -   Apply the mac-CellGroupConfig of MCG received in the 2nd message        to Target MCG MAC entity (575).    -   Apply the MAC parameters included in sl-ConfigDedicatedNR of the        received 2nd message to the Target MCG MAC entity. Target MCG        MAC entity performs operation related to SL communication        according to the configured parameters (580).    -   Initiate random access towards the target SpCell.    -   If T304 expires and RLF is not detected on source PCell (585):        -   apply the MAC parameters included in sl-ConfigDedicatedNR            received in the 1st message to the source MCG MAC entity.            Source MCG MAC entity performs operation related to SL            communication according to the configured parameters.        -   Release the target MCG MAC entity.    -   If T304 expires and RLF is detected on source PCell (590):        -   Release the target MCG MAC entity;        -   initiate RRC Connection Re-establishment. Source MCG MAC            entity is reset and source MCG MAC configuration is            released.    -   If DAPS HO is successfully completed (i.e. random access        procedure on target SpCell is successfully completed before the        T304 expires): release sl-ConfigDedicatedNR received in first        message (595).

Here, operation for MAC reset is described:

If a reset of the MAC entity is requested by upper layers, the MACentity shall:

-   -   initialize Bj for each logical channel to zero;    -   stop (if running) all timers;    -   consider all timeAlignmentTimers as expired and perform the        corresponding actions;    -   set the new data indicators (NDIs) for all uplink HARQ processes        to the value 0;    -   sets the NDIs for all HARQ process IDs to the value 0 for        monitoring PDCCH in Sidelink resource allocation mode 1;    -   stop, if any, ongoing RACH procedure;    -   discard explicitly signaled contention-free Random Access        Resources for 4-step RA type and 2-step RA type, if any;    -   flush Msg3 buffer;    -   flush MSGA buffer;    -   cancel, if any, triggered Scheduling Request procedure;    -   cancel, if any, triggered Buffer Status Reporting procedure;    -   cancel, if any, triggered Power Headroom Reporting procedure;    -   cancel, if any, triggered consistent listen-before-talk (LBT)        failure;    -   cancel, if any, triggered BFR;    -   cancel, if any, triggered Sidelink Buffer Status Reporting        procedure;    -   flush the soft buffers for all DL HARQ processes;    -   for each DL HARQ process, consider the next received        transmission for a TB as the very first transmission;    -   release, if any, Temporary C-RNTI;    -   reset all BFI_COUNTERs;    -   reset all LBT_COUNTERs.

Here, operation performed for partial MAC reset is described:

If a partial reset of the MAC entity is requested by upper layers, theMAC entity shall:

-   -   sets the NDIs for all HARQ process IDs to the value 0 for        monitoring PDCCH in Sidelink resource allocation mode 1;    -   cancel, if any, triggered Sidelink Buffer Status Reporting        procedure;    -   cancel, if any, triggered Scheduling Request procedure for        sidelink    -   flush the soft buffers for all Sidelink processes    -   Stop (if running) all timers related to Sidelink

In another method of this disclosure the UE operation is describedbelow.

1. UE is in RRC_CONNECTED state. There is a MAC entity for each CG (MCGand SCG) which performs the MAC operation for the respective CG. Notethat if SCG is not configured, there will be only one MAC entity i.e.MAC entity for MCG.

2. UE receives the first RRCReconfiguration message from gNB where themessage includes sl-ConfigDedicatedNR IE. sl-ConfigDedicatedNR IEincludes the dedicated SL communication parameters/configuration.

3. UE applies the MAC parameters included in sl-ConfigDedicatedNR ofreceived first message to the MCG MAC entity. MAC performs operationrelated to SL communication according to the configured parameters.

4. UE receives 2nd RRCReconfiguration message where the message includesReconfigurationWithSync IE for MCG and sl-ConfigDedicatedNR IE.

5. Upon receiving the second message, UE checks if there is at least oneDAPS bearer in radio bearer

configuration in received 2nd message.

6. if there is no DAPS bearer in radio bearer configuration in receivedsecond message, UE perform the following operation:

-   -   Start the timer T304    -   Reset the MCG MAC entity. Operations for MAC reset are described        later.    -   Apply the mac-CellGroupConfig of MCG received in the 2nd message        to MCG MAC entity    -   Apply the MAC parameters included in sl-ConfigDedicatedNR of        received 2nd message to the MCG MAC entity. MCG MAC entity        performs operation related to SL communication according to the        configured parameters.    -   Release sl-ConfigDedicatedNR received in first message    -   Initiate random access towards the target SpCell.    -   If T304 expires: initiate RRC Connection Re-establishment        wherein the MCG MAC entity is reset and MCG MAC configuration is        released.

7. if there is at least one DAPS bearer in radio bearer configuration inreceived second message, UE perform the following operation:

-   -   Start the timer T304    -   Create a new MCG MAC entity (‘referred as target MCG MAC        entity’). The existing MAC entity is referred as source MCG MAC        entity    -   Perform partial reset of source MCG MAC entity. Operation for        partial MAC reset are described earlier.    -   Apply the mac-CellGroupConfig of MCG received in the 2nd message        to Target MCG MAC entity    -   Apply the MAC parameters included in sl-ConfigDedicatedNR of the        received 2nd message to the Source MCG MAC entity. Source MCG        MAC entity performs operation related to SL communication        according to the configured parameters. In this embodiment, the        MAC parameters included in sl-ConfigDedicatedNR received in the        2nd message is applied to the source MCG MAC entity, instead of        target MCG MAC entity of FIG. 5A and FIG. 5B.    -   Initiate random access towards the target SpCell.    -   If T304 expires and RLF is not detected on source PCell:        -   Perform partial reset of source MCG MAC entity (optional,            may not be done in one embodiment)        -   apply the MAC parameters included in sl-ConfigDedicatedNR            received in the 1st message to the source MCG MAC entity.            Source MCG MAC entity performs operation related to SL            communication according to the configured parameters.        -   Release the target MCG MAC entity    -   If T304 expires and RLF is detected on source PCell:        -   Release the target MCG MAC entity;        -   initiate RRC Connection Re-establishment. Source MCG MAC            entity is reset and source MCG MAC configuration is            released.    -   If DAPS HO is successfully completed (i.e. random access        procedure on target SpCell is successfully completed before the        expiry of T304): release sl-ConfigDedicatedNR received in first        message

Embodiment 2—Paging Handling for MUSIM

In the 4G wireless communication system like LTE, there are deviceswhich have Multi Universal Subscriber Identity Module (MUSIM)capability, including dual SIM devices. The dual SIM devices operationis transparent to the network and certain procedures like pagingmonitoring and responding to paging, measurements, system informationacquisition etc. are currently handled in implementation specific way.In other words, there is no standard support for efficiently handlingthe aforementioned procedures. This has resulted not only in degradationof user experience in terms of loss of data throughput but also wastageof network resources. The dual SIM devices have different radiofrequency transmit-receive (RF Tx/Rx) capability and the implementationspecific solutions to handle the aforementioned procedures are not samebut depend on the RF capability of the dual SIM device. Depending on theRF Tx/Rx capability following types of dual SIM devices are available a)Dual SIM Dual Standby (DSDS) with single Tx/Rx RF capability, Dual SIMDual Receive (DSDR) with single Tx and dual Rx RF capability and DualSIM Dual Active (DSDA) with dual Tx/Rx RF capability.

The term dual SIM and MUSIM User Equipment (UE) or device is usedinterchangeable throughout the disclosure. The dual SIM device isrequired to monitor the paging occasion and other time criticaloccasions such as essential SIBs, Cell Broadcast Information, MultimediaBroadcast Multicast Services (MBMS) and the like, on the respectivesystem (network) associated with each USIM. In general, system with eachUSIM independently decides these occasions. The paging or SI occasion ofone USIM may collide with paging and other time critical occasions ofother USIMs. These collisions are handled in a specific manner accordingto UE implementations as there is no standard mechanism devised forMUSIM UE from the 3GPP standardization perspective. Therefore, this maysometime result in missing of the paging or time critical occasions forhandling of paging collisions for MUSIM devices. Recently, there isdiscussion within the 3GPP standardization to specify enablers to handlethe aforementioned procedures regardless of the UE RF capability. Thiswould be applicable to LTE system connected to EPC and NR systemconnected to 5GC. For e.g. a UE may support dual SIM capabilityassociated with Global System for Mobile Communication (GSM)+GSM,GSM+LTE, LTE+LTE, LTE+Voice over LTE (VoLTE), VoLTE+VoLTE, VoLTE+NR,LTE+NR, NR+NR so on and so forth.

The embodiment herein is to disclose methods and system for achievingefficiently handling of paging procedure and system informationacquisition by the dual SIM/MUSIM devices regardless of the Tx/Rxcapability. This is applicable when the device is registered on evolvedpacket core (EPC) through both SIMs, registered on 5G core (5GC) throughboth SIMs or registered on EPC through one SIM and registered on 5GCthrough the other SIM. The embodiments in the disclosure are illustratedusing dual SIM as an example but can be extended further to plurality ofSIMs.

In the current design, paging collision occurs if UE's PO in network Aoverlaps in time with UE's PO in network B. UE send indication tonetwork B to change its PO. Network may provide a new 5G S-TMSI. UE canindicate an offset for determining new PO. The offset can be used todetermine a new UE ID where UE is used to determine PF/PO.

-   -   In RRC_IDLE/INACTIVE state, UE monitors one PO every DRX cycle        T, where T=min (Default Paging Cycle, UE specific paging cycle)    -   UE determines its PF/PO based on UE ID where UE ID=5G S-TMSI mod        1024        -   If offset is applied, new UE ID=(5G S-TMSI+offset) mod 1024            or new UE ID=[[5G S-TMSI mod 1024]+Offset] mod 1024    -   system frame number (SFN) for the PF is determined by:        -   (SFN+PF offset) mod T=(T div N)*(UE_ID mod N)    -   Index (i_s), indicating the index of the PO is determined by:        -   i_s=floor (UE_ID/N) mod Ns, Ns is number of POs per PF, up            to 4    -   In PO, UE monitors PDCCH addressed to P-RNTI

FIGS. 6, 7, and 8 illustrate examples of paging collision between MUSIMaccording to various embodiments of the disclosure.

In NR, PO is the occasion in which UE receives PDCCH addressed toP-RNTI. The slot of PDSCH including paging message is indicated by PDCCHaddressed to P-RNTI. So even if UE's PO of network A and network B donot overlap, UE may still not be able to receive paging in one of thenetworks. See examples below where there is no overlapping between POsbut UE cannot receive paging message.

Referring to FIG. 6 , it illustrates an example of an overlappingbetween LTE PO (NW1) and NR PDSCH (NW 2)

Referring to FIG. 7 , it illustrates an example of an overlappingbetween NR PO (NW 1) and NR PDSCH (NW 2)

Referring to FIG. 8 , it illustrates an example of an overlappingbetween NR PDSCH (NW 1) and NR PDSCH (NW 2)

Embodiment 2-1

-   -   UE supports multiple SIMs where network (NW) A is LTE and NW B        is NR    -   UE is monitoring paging in both NW A and NW B    -   Starting slot of PO is slot ‘n’ in NW B    -   Maximum value of K0 in PDSCH-TimeDomainResourceAllocationList        received in SIB of NW B is ‘p’    -   Trigger condition to request for PO change wherein the condition        take into account the slot of PO and candidate slot(s) for        paging message in NR:        -   If any of the slot ‘n’ to ‘slot ‘n+p’ overlaps with LTE PO,            UE send indication to NW B to relocate its PO or UE send            indication to NW B to inform that it cannot receive paging            due to paging monitoring in another SIM.

Embodiment 2-2

-   -   UE supports multiple SIMs where NW A is NR and NW B is NR    -   UE is monitoring paging in both NW A and NW B    -   Starting slot of PO is slot ‘n’ in NW B. Maximum value of K0 in        PDSCH-TimeDomainResourceAllocationList received in SIB of NW B        is ‘p’    -   Starting slot of PO is slot ‘n1’ in NW A. Maximum value of K0 in        PDSCH-TimeDomainResourceAllocationList received in SIB of NW A        is ‘p1’    -   If any of the slot ‘n’ to ‘slot ‘n+p’ in NW B overlaps with slot        ‘n1’ to ‘slot ‘n1+p1’, UE sends indication to NW B to relocate        its PO or UE send indication to NW B to inform that it cannot        receive paging due to paging monitoring in another SIM.

Embodiment 2-3

-   -   UE supports multiple SIMs where NW A is LTE and NW B is NR    -   UE is monitoring paging in both NW A and NW B    -   Starting slot of PO is slot ‘n’ in NW B    -   Value of K0 used for paging a MUSIM UE is received in SIB of        NW B. Let's say the value is ‘q’.        -   gNB shall indicate this K0 in DCI of PDCCH addressed to            P-RNTI if scheduled paging message includes page for a MUSIM            UE. Whether page is for MUSIM UE or not can be indicated by            AMF to GNB in paging message    -   If any/both of the slot ‘n’ or ‘slot ‘n+q’ overlaps with LTE PO,        UE sends indication to NW B to relocate its PO or UE send        indication to NW B to inform that it cannot receive paging due        to paging monitoring in another SIM.

Embodiment 2-4

-   -   UE supports multiple SIMs where NW A is LTE and NW B is NR    -   UE is monitoring paging in both NW A and NW B    -   Starting slot of PO is slot ‘n’ in NW B. Value of K0 used for        paging a MUSIM UE is received in SIB of NW B. Let's say the        value is ‘q’.    -   Starting slot of PO is slot ‘n1’ in NW A. Value of K0 used for        paging a MUSIM UE is received in SIB of NW A. Let's say the        value is ‘q1’.    -   If any/both of the slot ‘n’ and ‘slot ‘n+p’ in NW B overlaps        with slot ‘n1’ or ‘slot ‘n1+q1’ in NW A, UE send indication to        NW B to relocate its PO or UE send indication to NW B to inform        that it cannot receive paging due to paging monitoring in        another SIM.

Embodiment 3—MAC PDU Generation

FIG. 9 illustrates an example of generating MAC PDU according to anembodiment of the disclosure.

Referring to FIG. 9 , in one method of this disclosure, for small datatransmission (SDT) in RRC_INACTIVE using MsgA or Msg3 or preconfiguredPUSCH resource, none of the LCH restrictions are applied whilegenerating MAC PDU. However, only the logical channels of RBs for whichSDT is enabled and have data available for transmission are used togenerate MAC PDU.

The UE operation for generating MAC PDU for an UL grant is as follows:

1. UE receives or is configured with an UL grant for new transmission(910).

2. UE checks if the UL grant is for SDT (920). In other words, UE checkwhether SDT procedure is ongoing (SDT procedure can be consideredongoing if SDT timer is running, SDT timer is started when SDT procedureis initiated.

3. If yes, none of the LCH restrictions are applied while generating MACPDU. Only the logical channels of RBs for which SDT is enabled and havedata available for transmission are used to generate MAC PDU. UE selectonly the logical channels of RBs for which SDT is enabled for MAC PDUgeneration (930). Note that MAC CE(s) may be included as well. RBs forwhich SDT is enabled is signaled by gNB in RRC signaling. Logicalchannels of SRB0 and SRB1 can be also considered for MAC PDU generation.UE applies LCP procedure for the selected logical channels (940).

4. If no, UE selects the logical channels which are allowed to betransmitted in this UL grant according to allowedSCS-List,maxPUSCH-Duration, configuredGrantType1Allowed, allowedServingCells,allowedCG-List and allowedPHY-PriorityIndex for MAC PDU generation(950).

FIG. 10 illustrates another example of generating MAC PDU according toan embodiment of the disclosure.

Referring to FIG. 10 , in another method of this disclosure, the methodfor selecting logical channels for SDT is performed by applyingallowedSCS-List and maxPUSCH-Duration for generating MAC PDU for SDT.This means that if LCH of RB for which SDT is enabled and is configuredwith allowedSCS-List and SCS included in allowedSCS-List is not the SCSof UL grant used for SDT, this LCH is not selected for SDT. This meansthat if LCH of RB for which SDT is enabled and is configured withmaxPUSCH-Duration and duration included in allowedSCS-List is not theduration of UL grant used for SDT, this LCH is not selected for SDT.AllowedServingCells is not applied for generating MAC PDU for SDT.ConfiguredGrantType1Allowed is not applied for RACH based small datatransmission but applied for non RACH based small data transmission. Fornon RACH based small data transmission, if LCH is not configured withconfiguredGrantType1Allowed, this LCH is not selected for SDT. LCH of RBfor which SDT is not enabled is not selected for SDT.

1. UE receives or is configured with an UL grant for new transmission(1010).

2. UE checks if the UL grant is for SDT (1020). In other words, UE checkwhether SDT procedure is ongoing.

3. If yes, UE checks whether if the UL grant is a pre-configured ULgrant (1030). If no, UE selects the logical channels which are allowedto be transmitted in this UL grant according to allowedSCS-List,maxPUSCH-Duration, configuredGrantType1Allowed, allowedServingCells,allowedCG-List, and allowedPHY-PriorityIndex for MAC PDU generation(1070).

4. If the UL grant is a pre-configured UL grant (1030), UE selects thelogical channels for which SDT is enabled and which are allowed to betransmitted in this UL grant, according to allowedSCS-List,maxPUSCH-Duration, configuredGrantType1 Allowed (1060). Logical channelsof SRB0 and SRB1 can be also considered for MAC PDU generation.

5. If the UL grant is not a pre-configured UL grant (1030), UE selectsthe logical channels of RBs for which SDT is enabled and which areallowed to be transmitted in this UL grant, according toallowedSCS-List, maxPUSCH-duration (1040). Logical channels of SRB0 andSRB1 can be also considered for MAC PDU generation.

6. And, UE applies LCP procedure for the selected logical channels(1050).

In another embodiment, network indicates whether to apply LCHrestrictions or not. Indication can be in RRCRelease or RACHconfiguration for SDT. If network indicates to apply LCH restrictions,all LCH restrictions are considered while selecting LCH for SDT. Inanother embodiment, which restrictions to apply can also be indicated bythe network. In this case, UE only applies the indicated LCHrestrictions while selecting LCH for SDT.

Here, monitoring of network response for SDT using CG resource isdescribed.

Upon performing UL transmission in CG resource for SDT, UE needs tomonitor DL for network response. Network response can include resourcefor retransmission/new transmission, DL data or RRC message to completeSDT procedure. For network response following aspects needs to beconsidered.

UE needs to know search space for monitoring PDCCH. One of the followingcan be considered for determining search space for monitoring PDCCH.

-   -   Option 1: sdt-SearchSpace can be signaled by network in        RRCRelease message.        -   1-1: sdt-SearchSpace indicates one of the search space in            PDCCH-ConfigCommon of initial DL BWP.        -   1-2: sdt-SearchSpace indicates one of the search space in            PDCCH-Config of initial DL BWP.    -   Option 2: sdt-SearchSpace can be signaled by network in initial        DL BWP configuration (PDCCH-ConfigCommon or PDCCH-Config).    -   Option 3: rar-SearchSpace is used by UE for monitoring PDCCH. Or        if sdt-SearchSpace is not configured UE monitors PDCCH in        rar-SearchSpace.

Here, RRC message for RRC based SDT is described.

During SDT, uplink data is transmitted in Msg3/MsgA/CG. gNB receivinguplink data in Msg3/MsgA/CG needs to identify the UE, identify the lastserving gNB (if the gNB to which UE is transmitting UL data is differentfrom the GNB where UE has last received RRCRelease with suspendconfiguration) to retrieve the UE's context and authenticate the UE. Inorder to do so, additional information (such as those listed below)needs to be transmitted along with uplink data in Msg3/MsgA/CG:

-   -   Resume Identity (short or full I-RNTI) to identity the UE's        context and last serving gNB (if the gNB to which UE is        transmitting UL data is different from the GNB where UE has last        received RRCRelease with suspend configuration).    -   Authentication token (i.e. resumeMAC-I) to authenticate UE.

One may argue that in case of SDT using dedicated CG, Resume Identity(short or full I-RNTI) to identity the UE's context and last serving gNBis not needed as the gNB can identify UE based on CG in which uplinkdata is received and the last serving gNB is the current gNB as UEperforms SDT using CG only if cell is not changed (i.e. camped cell issame the cell to which UE was last connected). However, Authenticationtoken is still needed to authenticate UE in RRC_INACTIVE.

The Resume Identity and resumeMAC-I is included inRRCResumeRequest/RRCResumeRequest1 messages. Instead of defining newmechanism to carry Resume Identity and resumeMAC-I,RRCResumeRequest/RRCResumeRequest1 message can be transmitted along withuplink data in Msg3/MsgA/CG. This is a simple approach and reducesspecification effort.

An alternate approach would be to define new RRC message(s) i.e.RRCResumeRequestSDT and RRCResumeRequest1SDT. The RRCResumeRequestSDTincludes Short Resume Identity and resumeMAC-I. Short Resume Identity isoptional and is included for RACH based SDT procedure and not includedfor CG based SDT procedure. The RRCResumeRequest1SDT includes LongResume Identity and resumeMAC-I. Since SDT is used only for MO, resumecause may not be needed as well. For new message network can alwaysassume that resumeCause is MO-Data. Cumulative UL buffer size or datavolume for DRBs for which SDT is enabled can be included in the RRCmessage. For CG based SDT procedure, RRCResumeRequestSDT message istransmitted without Short Resume Identity. For RACH based SDT procedure,RRCResumeRequestSDT or RRCResumeRequestSDT1 is transmitted depending onwhether short or long resume identity is needed respectively. Whether tosend short or long resume identity is indicated by GNB in systeminformation. In an alternate embodiment, RRCResumeRequest1 can be usedinstead of RRCResumeRequestSDT1.

Embodiment 4—msgATransMax Handling for 2 Step RA Based SDT Procedure

2 step RA procedure is initiated for SDT. UE initializes the preambletransmission counter (PREAMBLE_TRANSMISSION_COUNTER) to zero.

Step 1: If contention Free Random Access Resources are provided by gNBand there is at least one SSB/CSI-RS having SS-RSRP/CSI-RSRP above athreshold amongst the SSBs/CSI-RSs for which contention free randomaccess resources are provided, UE Transmit Random Access Preamble inPRACH occasion and MAC PDU in PUSCH Occasion using the assignedcontention free random access resources. Otherwise, UE transmit RandomAccess Preamble in PRACH occasion and MAC PDU in PUSCH Occasion usingthe contention based random access resources. In an embodiment, it ispossible that a valid PUSCH occasion is not available corresponding toselected SSB/CSI-RS and in this case UE skips transmission of MsgA MACPDU.

Step 2: UE then starts msgB-ResponseWindow and monitor the PDCCH forrandom access response in msgB-ResponseWindow. UE monitors the PDCCH ofthe SpCell for a random access response identified by MSGB-RNTI whilethe msgB-ResponseWindow is running. If C-RNTI MAC CE was included in theMSGA: UE additionally monitor the PDCCH of the SpCell for random accessresponse identified by the C-RNTI while the msgB-ResponseWindow isrunning.

Step 3: While msgB-ResponseWindow is running:

-   -   If C-RNTI was included in MsgA and UE receives PDCCH addressed        to C-RNTI and this random access procedure was initiated for        BFR: RAR reception is successful. RA procedure is successfully        completed. Go to step 8 below.    -   Else If C-RNTI was included in MsgA and TAT timer associated        with primary timing advance group (PTAG) is running and UE        receives PDCCH addressed to C-RNTI and this PDCCH contains UL        grant for new transmission: RAR reception is successful. RA        procedure is successfully completed. UE releases the 2 step CFRA        resources (random access preamble(s), RACH occasions, PUSCH        resources) configured (if any) for this random access procedure.        Release here means that UE will not use these resources for        subsequent random access procedure. Go to step 8 below. In an        embodiment, release operation may not be performed in this case,        as contention free resources may not be configured for the case        where PTAG is running and RA is initiated for events other than        BFR.    -   Else If C-RNTI was included in MsgA and TAT timer associated        with PTAG is not running and UE receives PDCCH addressed to        C-RNTI and DL TB scheduled by this PDCCH includes Absolute        timing advanced command MAC CE: RAR reception is successful. RA        procedure is successfully completed. UE releases the 2 step CFRA        resources (random access preamble(s), RACH occasions, PUSCH        resources) configured (if any) for this random access procedure.        Go to step 8. Release here means that UE will not use these        resources for subsequent random access procedure.

Else If UE receives PDCCH addressed to MSGB-RNTI and decoded TB includesfallbackRAR MAC subPDU corresponding to its transmitted preamble: RARreception is successful.

-   -   If random access preamble transmitted is contention free random        access preamble: RA procedure is successfully completed. UE        releases the 2 step CFRA resources (random access preamble(s),        RACH occasions, PUSCH resources) configured (if any) for this        random access procedure. Go to step 8. Release here means that        UE will not use these resources for subsequent random access        procedure.    -   Else        -   Transmit MsgA MAC PDU as Msg3 in UL grant received in            fallbackRAR.        -   Start contention resolution timer.        -   Go to step 5 below.    -   Else If UE receives PDCCH addressed to MSGB-RNTI and decoded TB        includes successRAR MAC subPDU corresponding to UE's contention        resolution identity (i.e. contention resolution identity        received matches the first 48 bits of CCCH SDU transmitted in        MsgA): RAR reception is successful. RA procedure is successfully        completed. Go to step 8. Note that this is the case when CCCH        SDU is included in MSGA, that is UE is in idle/inactive or        performing RRC connection re-establishment. For these cases        contention free resources are not configured, so no need to        release. In an alternate embodiment, UE releases the 2 step CFRA        resources (random access preamble(s), RACH occasions, PUSCH        resources) configured (if any) for this random access procedure.        Release here means that UE will not use these resources for        subsequent random access procedure.

Step 4: If RAR window expires:

-   -   Increment preamble transmission counter by 1.        -   If msgATransMax is configured, and if            PREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:            -   If 4 step random access resources for SDT are                configured:                -   Switch to 4 step RA and continue SDT procedure. Go                    to step 7.            -   Else                -   Terminate the ongoing SDT procedure and initiate                    normal connection resume procedure.    -   Else:        -   go to step 1.

(Alternate) Step 4: If RAR window expires:

-   -   Increment preamble transmission counter by 1.    -   If this RA procedure is not initiated for SDT and If        msgATransMax is configured, and if        PREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:        -   Switch to 4 step RA.    -   Else:        -   go to step 1.

(Alternate) Step 4: If RAR window expires:

-   -   Increment preamble transmission counter by 1.        -   If msgATransMax is configured, and if            PREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:        -   If this RA procedure is not initiated for SDT: Switch to 4            step RA.        -   If this RA procedure is initiated for SDT: Terminate the            ongoing SDT procedure and initiate normal connection resume            procedure.    -   Else:        -   go to step 1.

Step 5: While contention resolution timer is running:

-   -   If the Random Access procedure was initiated for beam failure        recovery and the UE receives PDCCH transmission addressed to the        C-RNTI; or if the Random Access procedure was initiated by a        PDCCH order and the UE receives PDCCH transmission addressed to        the C-RNTI; or if the Random Access procedure was initiated by        the MAC sublayer itself or by the RRC sublayer and the UE        receives PDCCH transmission addressed to the C-RNTI and contains        a UL grant for a new transmission: Contention Resolution is        successful; RA procedure is successfully completed. Release 2        step CFRA Resources i.e. preambles/ROs/PUSCH Resources        configured (if any) for this RA procedure. Go to step 8. Release        here means that UE will not use these resources for subsequent        random access procedure.

Step 6: If contention resolution timer expires:

-   -   Increment preamble transmission counter by 1.        -   If msgATransMax is configured, and if            PREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:            -   If 4 step random access resources for SDT are                configured:                -   Switch to 4 step RA and continue SDT procedure. Go                    to step 7 below.            -   Else                -   Terminate the ongoing SDT procedure and initiate                    normal connection resume procedure.    -   Else:        -   go to step 1.

(Alternate) Step 6: If contention resolution timer expires:

-   -   Increment preamble transmission counter by 1.    -   If this RA procedure is not initiated for SDT and If        msgATransMax is configured, and if        PREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:        -   Switch to 4 step RA.    -   Else:        -   go to step 1

(Alternate) Step 6: If contention resolution timer expires:

-   -   Increment preamble transmission counter by 1.        -   If msgATransMax is configured, and if            PREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:            -   If this RA procedure is not initiated for SDT: Switch to                4 step RA.            -   If this RA procedure is initiated for SDT: Terminate the                ongoing SDT procedure and initiate normal connection                resume procedure    -   Else:        -   go to step 1

Step 7: perform 4 step RA for SDT.

Step 8: Stop.

FIG. 11 is a block diagram of a terminal according to an embodiment ofthe disclosure.

Referring to FIG. 11 , a terminal includes a transceiver 1110, acontroller 1120 and a memory 1130. The controller 1120 may refer to acircuitry, an application-specific integrated circuit (ASIC), or atleast one processor. The transceiver 1110, the controller 1120 and thememory 1130 are configured to perform the operations of the terminalillustrated in the FIG. 1 to 10 , or described above. Although thetransceiver 1110, the controller 1120 and the memory 1130 are shown asseparate entities, they may be realized as a single entity like a singlechip. Or, the transceiver 1110, the controller 1120 and the memory 1130may be electrically connected to or coupled with each other.

The transceiver 1110 may transmit and receive signals to and from othernetwork entities, e.g., a base station.

The controller 1120 may control the terminal to perform functionsaccording to one of the embodiments described above. For example, thecontroller 1120 controls the transceiver 1110 and/or memory 1130 toperform small data transmission and reception according to variousembodiments of the disclosure.

In an embodiment, the operations of the terminal may be implementedusing the memory 1130 storing corresponding program codes. Specifically,the terminal may be equipped with the memory 1130 to store program codesimplementing desired operations. To perform the desired operations, thecontroller 1120 may read and execute the program codes stored in thememory 1130 by using at least one processor or a CPU.

FIG. 12 is a block diagram of a base station according to an embodimentof the disclosure.

Referring to FIG. 12 , a base station includes a transceiver 1210, acontroller 1220 and a memory 1230. The controller 1220 may refer to acircuitry, an ASIC, or at least one processor. The transceiver 1210, thecontroller 1220 and the memory 1230 are configured to perform theoperations of the base station illustrated in the FIG. 1 to 10 , ordescribed above. Although the transceiver 1210, the controller 1220 andthe memory 1230 are shown as separate entities, they may be realized asa single entity like a single chip. Or, the transceiver 1210, thecontroller 1220 and the memory 1230 may be electrically connected to orcoupled with each other.

The transceiver 1210 may transmit and receive signals to and from othernetwork entities, e.g., a terminal or a UE.

The controller 1220 may control the base station to perform functionsaccording to one of the embodiments described above. For example, thecontroller 1220 controls the transceiver 1210 and/or memory 1230 toperform small data transmission and reception according to variousembodiments of the disclosure.

In an embodiment, the operations of the base station may be implementedusing the memory 1230 storing corresponding program codes. Specifically,the base station may be equipped with the memory 1230 to store programcodes implementing desired operations. To perform the desiredoperations, the controller 1220 may read and execute the program codesstored in the memory 1230 by using at least one processor or a CPU.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: receiving, from a sourcebase station, a first radio resource control (RRC) message comprisinginformation on sidelink parameters for sidelink communication; applyingthe sidelink parameters included in the first RRC message to a firstmedium access control (MAC) entity associated with the source basestation; receiving, from the source base station, a second RRC messagecomprising reconfiguration with synchronization information andinformation on the sidelink parameters for sidelink communication;generating a second MAC entity associated with a target base station, incase that at least one dual active protocol stack (DAPS) bearer isconfigured in the second RRC message; applying the sidelink parametersincluded in the second RRC message to the second MAC entity associatedwith the target base station; and performing a random access procedurewith the target base station based on the second RRC message.
 2. Themethod of claim 1, further comprising: partially resetting the first MACentity, in case that the at least one DAPS bearer is configured in thesecond RRC message, wherein a partial reset of the first MAC entitycomprises: setting new data indicator (NDI) for all hybrid automaticrepeat request (HARQ) process identities to a value of 0 for monitoringa physical downlink control channel (PDCCH) in sidelink resourceallocation mode 1, cancelling triggered sidelink buffer status reporting(BSR) procedure, cancelling triggered scheduling request (SR) procedurefor sidelink, flushing soft buffers for all sidelink processes, andstopping all timers related to sidelink.
 3. The method of claim 1,further comprising: resetting the first MAC entity, in case that DAPSbearer is not configured in the second RRC message; applying thesidelink parameters included in the second RRC message to the first MACentity associated with the source base station; and releasing thesidelink parameters included in the first RRC message.
 4. The method ofclaim 1, wherein, in case that a T304 timer expires and a radio linkfailure (RLF) is not detected, the method further comprises: applyingthe sidelink parameters included in the first RRC message to the firstMAC entity associated with the source base station; and releasing thesecond MAC entity associated with the target base station.
 5. The methodof claim 1, wherein, in case that a T304 timer expires and a radio linkfailure (RLF) is detected, the method further comprises: releasing thesecond MAC entity associated with the target base station; andinitiating an RRC connection reestablishment procedure.
 6. A methodperformed by a source base station in a wireless communication system,the method comprising: transmitting, to a terminal, a first radioresource control (RRC) message comprising information on sidelinkparameters for sidelink communication, the sidelink parameters includedin the first RRC message are for a first medium access control (MAC)entity associated with the source base station; and transmitting, to theterminal, a second RRC message comprising reconfiguration withsynchronization information and information on the sidelink parametersfor sidelink communication, the sidelink parameters included in thesecond RRC message are for a second MAC entity associated with a targetbase station, wherein the second MAC entity is generated for the targetbase station, in case that at least one dual active protocol stack(DAPS) bearer is configured in the second RRC message, and wherein arandom access procedure is performed between the terminal and the targetbase station based on the second RRC message.
 7. The method of claim 6,wherein, in case that the at least one DAPS bearer is configured in thesecond RRC message, the first MAC entity is partially reset, and whereina partial reset of the first MAC entity comprises: setting new dataindicator (NDI) for all hybrid automatic repeat request (HARQ) processidentities to a value of 0 for monitoring a physical downlink controlchannel (PDCCH) in sidelink resource allocation mode 1, cancellingtriggered sidelink buffer status reporting (BSR) procedure, cancellingtriggered scheduling request (SR) procedure for sidelink, flushing softbuffers for all sidelink processes, and stopping all timers related tosidelink.
 8. The method of claim 6, wherein, in case that DAPS bearer isnot configured in the second RRC message, the first MAC entity is reset,the sidelink parameters included in the second RRC message are appliedto the first MAC entity, and the sidelink parameters included in thefirst RRC message are released.
 9. The method of claim 6, wherein, incase that a T304 timer expires and a radio link failure (RLF) is notdetected, the sidelink parameters included in the first RRC message areapplied to the first MAC entity, and the second MAC entity is released.10. The method of claim 6, wherein, in case that a T304 timer expiresand a radio link failure (RLF) is detected, the second MAC entity isreleased, and an RRC connection reestablishment procedure is initiated.11. A terminal in a wireless communication system, the terminalcomprising: a transceiver configured to transmit or receive a signal;and at least one processor configured to: receive, from a source basestation, a first radio resource control (RRC) message comprisinginformation on sidelink parameters for sidelink communication, apply thesidelink parameters included in the first RRC message to a first mediumaccess control (MAC) entity associated with the source base station,receive, from the source base station, a second RRC message comprisingreconfiguration with synchronization information and information on thesidelink parameters for sidelink communication, generate a second MACentity associated with a target base station, in case that at least onedual active protocol stack (DAPS) bearer is configured in the second RRCmessage, apply the sidelink parameters included in the second RRCmessage to the second MAC entity associated with the target basestation, and perform a random access procedure with the target basestation based on the second RRC message.
 12. The terminal of claim 11,wherein the at least one processor is further configured to partiallyreset the first MAC entity, in case that the at least one DAPS bearer isconfigured in the second RRC message, and wherein a partial reset of thefirst MAC entity comprises: setting new data indicator (NDI) for allhybrid automatic repeat request (HARQ) process identities to a value of0 for monitoring a physical downlink control channel (PDCCH) in sidelinkresource allocation mode 1, cancelling triggered sidelink buffer statusreporting (BSR) procedure, cancelling triggered scheduling request (SR)procedure for sidelink, flushing soft buffers for all sidelinkprocesses, and stopping all timers related to sidelink.
 13. The terminalof claim 11, wherein the at least one processor is further configuredto: reset the first MAC entity, in case that DAPS bearer is notconfigured in the second RRC message, apply the sidelink parametersincluded in the second RRC message to the first MAC entity associatedwith the source base station, and release the sidelink parametersincluded in the first RRC message.
 14. The terminal of claim 11,wherein, in case that a T304 timer expires and a radio link failure(RLF) is not detected, the at least one processor is further configuredto: apply the sidelink parameters included in the first RRC message tothe first MAC entity associated with the source base station, andrelease the second MAC entity associated with the target base station.15. The terminal of claim 11, wherein, in case that a T304 timer expiresand a radio link failure (RLF) is detected, the at least one processoris further configured to: release the second MAC entity associated withthe target base station, and initiate an RRC connection reestablishmentprocedure.
 16. A source base station in a wireless communication system,the source base station comprising: a transceiver configured to transmitor receive a signal; and at least one processor configured to: transmit,to a terminal, a first radio resource control (RRC) message comprisinginformation on sidelink parameters for sidelink communication, thesidelink parameters included in the first RRC message are for a firstmedium access control (MAC) entity associated with the source basestation, and transmit, to the terminal, a second RRC message comprisingreconfiguration with synchronization information and information on thesidelink parameters for sidelink communication, the sidelink parametersincluded in the second RRC message are for a second MAC entityassociated with a target base station, wherein the second MAC entity isgenerated for the target base station, in case that at least one dualactive protocol stack (DAPS) bearer is configured in the second RRCmessage, and wherein a random access procedure is performed between theterminal and the target base station based on the second RRC message.17. The source base station of claim 16, wherein, in case that the atleast one DAPS bearer is configured in the second RRC message, the firstMAC entity is partially reset, and wherein a partial reset of the firstMAC entity comprises: setting new data indicator (NDI) for all hybridautomatic repeat request (HARQ) process identities to a value of 0 formonitoring a physical downlink control channel (PDCCH) in sidelinkresource allocation mode 1, cancelling triggered sidelink buffer statusreporting (BSR) procedure, cancelling triggered scheduling request (SR)procedure for sidelink, flushing soft buffers for all sidelinkprocesses, and stopping all timers related to sidelink.
 18. The sourcebase station of claim 16, wherein, in case that DAPS bearer is notconfigured in the second RRC message, the first MAC entity is reset, thesidelink parameters included in the second RRC message are applied tothe first MAC entity, and the sidelink parameters included in the firstRRC message are released.
 19. The source base station of claim 16,wherein, in case that a T304 timer expires and a radio link failure(RLF) is not detected, the sidelink parameters included in the first RRCmessage are applied to the first MAC entity, and the second MAC entityis released.
 20. The source base station of claim 16, wherein, in casethat a T304 timer expires and a radio link failure (RLF) is detected,the second MAC entity is released, and an RRC connection reestablishmentprocedure is initiated.